This invention relates in general to cushions for seating and more particularly to a modular wheelchair cushion which has a shaped foam base, a fluid filled or foam cellular pad covering part of the base, and a fabric cover enclosing the base and the pad.
Those who must spend extended time in wheelchairs run the risk of tissue breakdown and the development of pressure sores, which are extremely dangerous and difficult to cure. These pressure sores are decubitus ulcers, typically formed in areas where bony prominences exist, such as the ischia, heels, elbows, ears and shoulders. Typically, when sitting much of the individual's weight concentrates in the regions of the ischia, that is at the bony prominences of the buttocks and unless frequent movement occurs, the flow of blood to the skin tissue in these regions decreases to the point that the tissue breaks down. This problem is well known and many forms of cushions are especially designed for wheelchairs for reducing the concentration of weight in the region of the ischia, and these cushions generally seek to distribute the user's weight more uniformly over a larger area of the buttocks.
Another area where problems occur is in the trochanter area and both cushions and bases for the cushions are shaped so that the thighs are loaded and pressure is relieved on the ischia and the trochanters. Still another problem with wheelchair type cushions is stabilization of the user so that he has a feeling of security when sitting in the wheelchair.
A number of patents show cellular cushions which comprise an array of closely spaced air cells which project upwardly from a common base and are interconnected. These cushions combine the most uniform distribution of weight and thus provide the greatest protection from the occurrence of pressure sores. Since the air cells communicate with each other, all exist at the same internal pressure and each air cell exerts essentially the same restoring force against the buttocks, irrespective of the extent to which it is deflected. U.S. Pat. No. 4,541,136 shows a cellular cushion currently manufactured and sold by Roho, Inc. of Belleville, Ill. for use on wheelchairs.
The stability problem has been attacked by the use of shaped bases such as shown in Graebe U.S. Pat. No. 4,953,913 and Jay U.S. Pat. No. 4,726,624. These bases are generally used in conjunction with cushions and Graebe U.S. Pat. No. 4,953,913 has been used in conjunction with a cellular cushion and a fabric cover. The stability problem also has been addressed in the cellular cushion field by the use of zoned areas of inflation as shown in Graebe U.S. Pat. No. 4,698,864 which shows a zoned cellular cushion with cells of varying height and Graebe U.S. Pat. No. 5,052,068 which shows another form of zoned cushions with cells of different heights.
Graebe U.S. Ser. No. 07/723,408, now U.S. Pat. No. 5,111,544 shows a cover for a zoned cellular cushion which keeps the cells from deflecting outwardly. This cover has a stretchable top, a skid resistant base and a non-stretchable fabric side panel area.
The present invention resides in a foamed base having a flat rear area onto which may be fastened a variety of pads, including those which have a shaped surface to conform to body shapes, preferably a pad formed with upstanding air inflated cells. The base has a raised shaped front designed to load the thighs and separate the legs to stabilize the pelvis. A fabric cover forms the outside of the composite cushion and has a portion of the top formed of stretchable material and the remainder of the top and sides formed of a slick non-stretchable fabric with a skid resistant base. The base by itself is useful by able bodied persons who have good tissue bulk around their legs, whereas disabled persons who do not have good thigh bulk benefit by having a fluid filled module, such as an inflated air module, or a suitable foam module installed on the rear area.
The invention also consists in the parts and in the arrangements and combinations of parts hereinafter described and claimed.